Have a x360 JD with Kawasaki engine FS 651V-ES05-R. Yesterday fill with fuel and started up to mow and began backing up and Backfired loud. Tried to restart and now just shoots out lots of gas from exhaust pipe and no start . Took out plugs and they fire but lots of gas coming from cylinders. Checked fuel celanoid and it is working fine. Called JD and talked to mech he told me need new engine . $1500 only 475 hrs . Any help or ideas would really help. Darrel